Relation of plasma dexamethasone to clinical response.

OBJECTIVE The clinical effects of high dosage pulse glucocorticosteroid (GS) infusion as a treatment for rheumatoid arthritis (RA) differ considerably between patients. The aim of the present study was to gain more insight into these differences in clinical response. METHODS Twenty-three RA patients (6 M/17 F) with treatment-resistant active erosive disease were treated with GS pulse therapy, consisting of 3 infusions of 200 mg dexamethasone at 3-day intervals. Plasma dexamethasone and plasma cortisol levels, as well as the mononuclear cell glucocorticosteroid receptor density, were determined on days 0, 2, 6, 12 and 40 after the start of therapy. Clinical evaluation consisted of the Thompson articular index, the erythrocyte sedimentation rate (ESR), and the serum concentration of C reactive protein (CRP). RESULTS Plasma dexamethasone levels in RA patients determined during pulse therapy revealed the existence of two groups. One group reached significantly (p < 0.05) higher plasma levels than another group comparable for age and sex. The CRP, ESR and Thompson joint score prior to the start of pulse therapy were all higher (p < 0.05) for the high plasma dexamethasone group. The decrease in ESR, CRP and the Thompson joint score was also significantly greater (all p < 0.05) for the high plasma dexamethasone group. Plasma cortisol, as well as the GS receptor density at the start of treatment, did not differ between the two groups; both decreased after the first pulse in both groups and returned to pre-treatment values shortly after the last infusion. CONCLUSION The treatment of refractory RA with dexamethasone pulse therapy is, on average, beneficial. The high plasma dexamethasone levels reached might depend on the greater severity of the disease in these patients prior to the start of the treatment, and result in greater changes in the disease parameters. Glucocorticosteroid receptor density measurements made during and directly after high dose pulse dexamethasone treatment proved to be unreliable because of the high plasma dexamethasone levels.